Serializable, Comparable<Float>, Constable, ConstantDesc
The
Float
class wraps a value of primitive type
float
in an object. An object of type
Float
contains a single field whose type is
float
.
In addition, this class provides several methods for converting a float to a String and a String to a float, as well as other constants and methods useful when dealing with a float.
This is a value-based class; programmers should treat instances that are equal as interchangeable and should not use instances for synchronization, or unpredictable behavior may occur. For example, in a future release, synchronization may fail.
Floating-point Equality, Equivalence, and ComparisonThe class
java.lang.Double
has a
discussion of equality, equivalence, and comparison of floating-point valuesthat is equally applicable to
float
values.
Fields
static final int
The number of bytes used to represent a float value.
static final int
Maximum exponent a finite float variable may have.
static final float
A constant holding the largest positive finite value of type float, (2-2-23)·2127.
static final int
Minimum exponent a normalized float variable may have.
static final float
A constant holding the smallest positive normal value of type float, 2-126.
static final float
A constant holding the smallest positive nonzero value of type float, 2-149.
static final float
A constant holding a Not-a-Number (NaN) value of type float.
static final float
A constant holding the negative infinity of type float.
static final float
A constant holding the positive infinity of type float.
static final int
The number of bits in the significand of a float value.
static final int
The number of bits used to represent a float value.
The Class instance representing the primitive type float.
Constructors
Deprecated, for removal: This API element is subject to removal in a future version. Deprecated, for removal: This API element is subject to removal in a future version. Deprecated, for removal: This API element is subject to removal in a future version.byte
Returns the value of this Float as a byte after a narrowing primitive conversion.
static int
Compares the two specified float values.
int
Compares two Float objects numerically.
Returns an
Optional
containing the nominal descriptor for this instance, which is the instance itself.
double
Returns the value of this Float as a double after a widening primitive conversion.
boolean
Compares this object against the specified object.
static float
Returns the float value closest to the numerical value of the argument, a floating-point binary16 value encoded in a short.
static short
Returns the floating-point binary16 value, encoded in a short, closest in value to the argument.
static int
Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout.
static int
Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout, preserving Not-a-Number (NaN) values.
float
Returns the float value of this Float object.
int
Returns a hash code for this Float object.
static int
Returns a hash code for a float value; compatible with Float.hashCode().
static float
Returns the float value corresponding to a given bit representation.
int
Returns the value of this Float as an int after a narrowing primitive conversion.
static boolean
Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).
boolean
Returns true if this Float value is infinitely large in magnitude, false otherwise.
static boolean
Returns true if the specified number is infinitely large in magnitude, false otherwise.
boolean
Returns true if this Float value is a Not-a-Number (NaN), false otherwise.
static boolean
Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.
long
Returns value of this Float as a long after a narrowing primitive conversion.
static float
Returns the greater of two
float
values as if by calling
Math.max
.
static float
Returns the smaller of two
float
values as if by calling
Math.min
.
static float
Returns a new float initialized to the value represented by the specified String, as performed by the valueOf method of class Float.
Resolves this instance as a
ConstantDesc
, the result of which is the instance itself.
short
Returns the value of this Float as a short after a narrowing primitive conversion.
static float
Adds two float values together as per the + operator.
Returns a hexadecimal string representation of the float argument.
Returns a string representation of this Float object.
Returns a string representation of the float argument.
Returns a Float instance representing the specified float value.
Returns a Float object holding the float value represented by the argument string s.
public static final float POSITIVE_INFINITY
A constant holding the positive infinity of type float. It is equal to the value returned by Float.intBitsToFloat(0x7f800000).
public static final float NEGATIVE_INFINITY
A constant holding the negative infinity of type float. It is equal to the value returned by Float.intBitsToFloat(0xff800000).
public static final float NaN
A constant holding a Not-a-Number (NaN) value of type float. It is equivalent to the value returned by Float.intBitsToFloat(0x7fc00000).
public static final float MAX_VALUE
A constant holding the largest positive finite value of type float, (2-2-23)·2127. It is equal to the hexadecimal floating-point literal 0x1.fffffeP+127f and also equal to Float.intBitsToFloat(0x7f7fffff).
public static final float MIN_NORMAL
A constant holding the smallest positive normal value of type float, 2-126. It is equal to the hexadecimal floating-point literal 0x1.0p-126f and also equal to Float.intBitsToFloat(0x00800000).
public static final float MIN_VALUE
A constant holding the smallest positive nonzero value of type float, 2-149. It is equal to the hexadecimal floating-point literal 0x0.000002P-126f and also equal to Float.intBitsToFloat(0x1).
public static final int SIZE
The number of bits used to represent a float value.
public static final int PRECISION
The number of bits in the significand of a
float
value. This is the parameter N in section
4.2.3of
The Java Language Specification.
public static final int MAX_EXPONENT
Maximum exponent a finite float variable may have. It is equal to the value returned by Math.getExponent(Float.MAX_VALUE).
public static final int MIN_EXPONENT
Minimum exponent a normalized float variable may have. It is equal to the value returned by Math.getExponent(Float.MIN_NORMAL).
public static final int BYTES
The number of bytes used to represent a float value.
The Class instance representing the primitive type float.
Constructs a newly allocated Float object that represents the primitive float argument.
value - the value to be represented by the Float.
Constructs a newly allocated Float object that represents the argument converted to type float.
value - the value to be represented by the Float.
Constructs a newly allocated Float object that represents the floating-point value of type float represented by the string. The string is converted to a float value as if by the valueOf method.
s - a string to be converted to a Float.
NumberFormatException - if the string does not contain a parsable number.
Returns a string representation of the
float
argument. All characters mentioned below are ASCII characters.
NaN".-' ('\u002D'); if the sign is positive, no sign character appears in the result. As for the magnitude m:
"Infinity"; thus, positive infinity produces the result "Infinity" and negative infinity produces the result "-Infinity"."0.0"; thus, negative zero produces the result "-0.0" and positive zero produces the result "0.0".A decimal is a number of the form s×10i for some (unique) integers s > 0 and i such that s is not a multiple of 10. These integers are the significand and the exponent, respectively, of the decimal. The length of the decimal is the (unique) positive integer n meeting 10n-1 ≤ s < 10n.
The decimal dm for a finite positive m is defined as follows:
The (uniquely) selected decimal dm is then formatted. Let s, i and n be the significand, exponent and length of dm, respectively. Further, let e = n + i - 1 and let s1…sn be the usual decimal expansion of s. Note that s1 ≠ 0 and sn ≠ 0. Below, the decimal point '.' is '\u002E' and the exponent indicator 'E' is '\u0045'.
0.0…0s1…sn, where there are exactly -(n + i) zeroes between the decimal point and s1. For example, 123 × 10-4 is formatted as 0.0123.0…0.0, where there are exactly i zeroes between sn and the decimal point. For example, 123 × 102 is formatted as 12300.0..sn+i+1…sn, where there are exactly -i digits to the right of the decimal point. For example, 123 × 10-1 is formatted as 12.3.Integer.toString(int).
.0Ee. For example, 1 × 1023 is formatted as 1.0E23..s2…snEe. For example, 123 × 10-21 is formatted as 1.23E-19.To create localized string representations of a floating-point value, use subclasses of NumberFormat.
f - the float to be converted.
Returns a hexadecimal string representation of the
float
argument. All characters mentioned below are ASCII characters.
NaN".-' ('\u002D'); if the sign is positive, no sign character appears in the result. As for the magnitude m:
"Infinity"; thus, positive infinity produces the result "Infinity" and negative infinity produces the result "-Infinity"."0x0.0p0"; thus, negative zero produces the result "-0x0.0p0" and positive zero produces the result "0x0.0p0".float value with a normalized representation, substrings are used to represent the significand and exponent fields. The significand is represented by the characters "0x1." followed by a lowercase hexadecimal representation of the rest of the significand as a fraction. Trailing zeros in the hexadecimal representation are removed unless all the digits are zero, in which case a single zero is used. Next, the exponent is represented by "p" followed by a decimal string of the unbiased exponent as if produced by a call to Integer.toString on the exponent value.float value with a subnormal representation, the significand is represented by the characters "0x0." followed by a hexadecimal representation of the rest of the significand as a fraction. Trailing zeros in the hexadecimal representation are removed. Next, the exponent is represented by "p-126". Note that there must be at least one nonzero digit in a subnormal significand.1.0 0x1.0p0 -1.0 -0x1.0p0 2.0 0x1.0p1 3.0 0x1.8p1 0.5 0x1.0p-1 0.25 0x1.0p-2 Float.MAX_VALUE 0x1.fffffep127 Minimum Normal Value 0x1.0p-126 Maximum Subnormal Value 0x0.fffffep-126 Float.MIN_VALUE 0x0.000002p-126
f - the float to be converted.
Returns a
Float
object holding the
float
value represented by the argument string
s
.
If s is null, then a NullPointerException is thrown.
Leading and trailing whitespace characters in s are ignored. Whitespace is removed as if by the String.trim() method; that is, both ASCII space and control characters are removed. The rest of s should constitute a FloatValue as described by the lexical syntax rules:
- FloatValue:
- Signopt
NaN- Signopt
Infinity- Signopt FloatingPointLiteral
- Signopt HexFloatingPointLiteral
- SignedInteger
- HexFloatingPointLiteral:
- HexSignificand BinaryExponent FloatTypeSuffixopt
- HexSignificand:
- HexNumeral
- HexNumeral
.0xHexDigitsopt.HexDigits0XHexDigitsopt.HexDigits
- BinaryExponent:
- BinaryExponentIndicator SignedInteger
- BinaryExponentIndicator:
pP
where
Sign,
FloatingPointLiteral,
HexNumeral,
HexDigits,
SignedIntegerand
FloatTypeSuffixare as defined in the lexical structure sections of
The Java Language Specification, except that underscores are not accepted between digits. If
s
does not have the form of a
FloatValue, then a
NumberFormatException
is thrown. Otherwise,
s
is regarded as representing an exact decimal value in the usual "computerized scientific notation" or as an exact hexadecimal value; this exact numerical value is then conceptually converted to an "infinitely precise" binary value that is then rounded to type
float
by the usual round-to-nearest rule of IEEE 754 floating-point arithmetic, which includes preserving the sign of a zero value. Note that the round-to-nearest rule also implies overflow and underflow behaviour; if the exact value of
s
is large enough in magnitude (greater than or equal to (
MAX_VALUE
+
ulp(MAX_VALUE)
/2), rounding to
float
will result in an infinity and if the exact value of
s
is small enough in magnitude (less than or equal to
MIN_VALUE
/2), rounding to float will result in a zero. Finally, after rounding a
Float
object representing this
float
value is returned.
To interpret localized string representations of a floating-point value, use subclasses of NumberFormat.
Note that trailing format specifiers, specifiers that determine the type of a floating-point literal (1.0f is a float value; 1.0d is a double value), do not influence the results of this method. In other words, the numerical value of the input string is converted directly to the target floating-point type. In general, the two-step sequence of conversions, string to double followed by double to float, is not equivalent to converting a string directly to float. For example, if first converted to an intermediate double and then to float, the string"1.00000017881393421514957253748434595763683319091796875001d"
results in the float value 1.0000002f; if the string is converted directly to float, 1.0000001f results.
To avoid calling this method on an invalid string and having a NumberFormatException be thrown, the documentation for Double.valueOf lists a regular expression which can be used to screen the input.
s - the string to be parsed.
Float object holding the value represented by the String argument.
NumberFormatException - if the string does not contain a parsable number.
Returns a
Float
instance representing the specified
float
value. If a new
Float
instance is not required, this method should generally be used in preference to the constructor
Float(float)
, as this method is likely to yield significantly better space and time performance by caching frequently requested values.
f - a float value.
Float instance representing f.
Returns a new float initialized to the value represented by the specified String, as performed by the valueOf method of class Float.
s - the string to be parsed.
float value represented by the string argument.
NullPointerException - if the string is null
NumberFormatException - if the string does not contain a parsable float.
public static boolean isNaN(float v)
Returns true if the specified number is a Not-a-Number (NaN) value, false otherwise.
v - the value to be tested.
true if the argument is NaN; false otherwise.
public static boolean isInfinite(float v)
Returns true if the specified number is infinitely large in magnitude, false otherwise.
v - the value to be tested.
true if the argument is positive infinity or negative infinity; false otherwise.
public static boolean isFinite(float f)
Returns true if the argument is a finite floating-point value; returns false otherwise (for NaN and infinity arguments).
f - the float value to be tested
true if the argument is a finite floating-point value, false otherwise.
public boolean isNaN()
Returns true if this Float value is a Not-a-Number (NaN), false otherwise.
true if the value represented by this object is NaN; false otherwise.
public boolean isInfinite()
Returns true if this Float value is infinitely large in magnitude, false otherwise.
true if the value represented by this object is positive infinity or negative infinity; false otherwise.
Returns a string representation of this Float object. The primitive float value represented by this object is converted to a String exactly as if by the method toString of one argument.
public byte byteValue()
Returns the value of this Float as a byte after a narrowing primitive conversion.
byteValue in class Number
float value represented by this object converted to type byte
public short shortValue()
Returns the value of this Float as a short after a narrowing primitive conversion.
shortValue in class Number
float value represented by this object converted to type short
public int intValue()
Returns the value of this Float as an int after a narrowing primitive conversion.
intValue in class Number
float value represented by this object converted to type int
public long longValue()
Returns value of this Float as a long after a narrowing primitive conversion.
longValue in class Number
float value represented by this object converted to type long
public float floatValue()
Returns the float value of this Float object.
floatValue in class Number
float value represented by this object
public double doubleValue()
Returns the value of this Float as a double after a widening primitive conversion.
doubleValue in class Number
float value represented by this object converted to type double
public int hashCode()
Returns a hash code for this
Float
object. The result is the integer bit representation, exactly as produced by the method
floatToIntBits(float)
, of the primitive
float
value represented by this
Float
object.
public static int hashCode(float value)
Returns a hash code for a float value; compatible with Float.hashCode().
value - the value to hash
float value.
Compares this object against the specified object. The result is
true
if and only if the argument is not
null
and is a
Float
object that represents a
float
with the same value as the
float
represented by this object. For this purpose, two
float
values are considered to be the same if and only if the method
floatToIntBits(float)
returns the identical
int
value when applied to each.
equals in class Object
floatToIntBits(float) rather than the == operator on float values since the == operator does not define an equivalence relation and to satisfy the equals contract an equivalence relation must be implemented; see this discussion for details of floating-point equality and equivalence.
obj - the object to be compared
true if the objects are the same; false otherwise.
public static int floatToIntBits(float value)
Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout.
Bit 31 (the bit that is selected by the mask 0x80000000) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask 0x7f800000) represent the exponent. Bits 22-0 (the bits that are selected by the mask 0x007fffff) represent the significand (sometimes called the mantissa) of the floating-point number.
If the argument is positive infinity, the result is 0x7f800000.
If the argument is negative infinity, the result is 0xff800000.
If the argument is NaN, the result is 0x7fc00000.
In all cases, the result is an integer that, when given to the intBitsToFloat(int) method, will produce a floating-point value the same as the argument to floatToIntBits (except all NaN values are collapsed to a single "canonical" NaN value).
value - a floating-point number.
public static int floatToRawIntBits(float value)
Returns a representation of the specified floating-point value according to the IEEE 754 floating-point "single format" bit layout, preserving Not-a-Number (NaN) values.
Bit 31 (the bit that is selected by the mask 0x80000000) represents the sign of the floating-point number. Bits 30-23 (the bits that are selected by the mask 0x7f800000) represent the exponent. Bits 22-0 (the bits that are selected by the mask 0x007fffff) represent the significand (sometimes called the mantissa) of the floating-point number.
If the argument is positive infinity, the result is 0x7f800000.
If the argument is negative infinity, the result is 0xff800000.
If the argument is NaN, the result is the integer representing the actual NaN value. Unlike the floatToIntBits method, floatToRawIntBits does not collapse all the bit patterns encoding a NaN to a single "canonical" NaN value.
In all cases, the result is an integer that, when given to the intBitsToFloat(int) method, will produce a floating-point value the same as the argument to floatToRawIntBits.
value - a floating-point number.
public static float intBitsToFloat(int bits)
Returns the
float
value corresponding to a given bit representation. The argument is considered to be a representation of a floating-point value according to the IEEE 754 floating-point "single format" bit layout.
If the argument is 0x7f800000, the result is positive infinity.
If the argument is 0xff800000, the result is negative infinity.
If the argument is any value in the range 0x7f800001 through 0x7fffffff or in the range 0xff800001 through 0xffffffff, the result is a NaN. No IEEE 754 floating-point operation provided by Java can distinguish between two NaN values of the same type with different bit patterns. Distinct values of NaN are only distinguishable by use of the Float.floatToRawIntBits method.
In all other cases, let s, e, and m be three values that can be computed from the argument:
int s = ((bits >> 31) == 0) ? 1 : -1;
int e = ((bits >> 23) & 0xff);
int m = (e == 0) ?
(bits & 0x7fffff) << 1 :
(bits & 0x7fffff) | 0x800000;
Then the floating-point result equals the value of the mathematical expression
s·
m·2
e-150.
Note that this method may not be able to return a float NaN with exactly same bit pattern as the int argument. IEEE 754 distinguishes between two kinds of NaNs, quiet NaNs and signaling NaNs. The differences between the two kinds of NaN are generally not visible in Java. Arithmetic operations on signaling NaNs turn them into quiet NaNs with a different, but often similar, bit pattern. However, on some processors merely copying a signaling NaN also performs that conversion. In particular, copying a signaling NaN to return it to the calling method may perform this conversion. So intBitsToFloat may not be able to return a float with a signaling NaN bit pattern. Consequently, for some int values, floatToRawIntBits(intBitsToFloat(start)) may not equal start. Moreover, which particular bit patterns represent signaling NaNs is platform dependent; although all NaN bit patterns, quiet or signaling, must be in the NaN range identified above.
bits - an integer.
float floating-point value with the same bit pattern.
public static float float16ToFloat(short floatBinary16)
Returns the
float
value closest to the numerical value of the argument, a floating-point binary16 value encoded in a
short
. The conversion is exact; all binary16 values can be exactly represented in
float
. Special cases:
The IEEE 754 standard defines binary16 as a 16-bit format, along with the 32-bit binary32 format (corresponding to the
float
type) and the 64-bit binary64 format (corresponding to the
double
type). The binary16 format is similar to the other IEEE 754 formats, except smaller, having all the usual IEEE 754 values such as NaN, signed infinities, signed zeros, and subnormals. The parameters (JLS
4.2.3) for the binary16 format are N = 11 precision bits, K = 5 exponent bits,
Emax= 15, and
Emin= -14.
floatBinary16 - the binary16 value to convert to float
float value closest to the numerical value of the argument, a floating-point binary16 value encoded in a short
public static short floatToFloat16(float f)
Returns the floating-point binary16 value, encoded in a
short
, closest in value to the argument. The conversion is computed under the
round to nearest even rounding mode. Special cases:
The
binary16 formatis discussed in more detail in the
float16ToFloat(short)
method.
f - the float value to convert to binary16
short, closest in value to the argument
Compares two
Float
objects numerically. This method imposes a total order on
Float
objects with two differences compared to the incomplete order defined by the Java language numerical comparison operators (
<, <=, ==, >=, >
) on
float
values.
Float.NaN to be equal to itself and greater than all other double values (including Float.POSITIVE_INFINITY).+0.0f), to be greater than negative zero (-0.0f).This ensures that the
natural orderingof
Float
objects imposed by this method is
consistent with equals; see
this discussionfor details of floating-point comparison and ordering.
compareTo in interface Comparable<Float>
anotherFloat - the Float to be compared.
0 if anotherFloat is numerically equal to this Float; a value less than 0 if this Float is numerically less than anotherFloat; and a value greater than 0 if this Float is numerically greater than anotherFloat.
<, <=, >, and >=
public static int compare(float f1, float f2)
Compares the two specified
float
values. The sign of the integer value returned is the same as that of the integer that would be returned by the call:
Float.valueOf(f1).compareTo(Float.valueOf(f2))
f1 - the first float to compare.
f2 - the second float to compare.
0 if f1 is numerically equal to f2; a value less than 0 if f1 is numerically less than f2; and a value greater than 0 if f1 is numerically greater than f2.
public static float sum(float a, float b)
Adds two float values together as per the + operator.
a - the first operand
b - the second operand
a and b
public static float max(float a, float b)
Returns the greater of two
float
values as if by calling
Math.max
.
a - the first operand
b - the second operand
a and b
public static float min(float a, float b)
Returns the smaller of two
float
values as if by calling
Math.min
.
a - the first operand
b - the second operand
a and b
Returns an
Optional
containing the nominal descriptor for this instance, which is the instance itself.
describeConstable in interface Constable
Optional describing the Float instance
Resolves this instance as a
ConstantDesc
, the result of which is the instance itself.
resolveConstantDesc in interface ConstantDesc
lookup - ignored
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